This invention relates in general to clutches and, more particularly, to clutches for the drive trains of automotive vehicles.
The drive train of the typical automobile equipped with a manual transmission includes a clutch interposed between the engine and the transmission to, of course, engage and disengage the engine from the drive wheels and to facilitate the change of gearing in the transmission. The clutch used almost universally on automobiles of current manufacture has a pair of friction surfaces--one on the flywheel and the other on a pressure plate that is carried by the flywheel--and a clutch disk which is located between the friction surfaces. The flywheel and the pressure plate, of course, rotate with the crankshaft of the engine, and the latter is biased toward the former under a force exerted by a spring, so that the clutch normally assumes an engaged condition in which the disk is clamped between the friction sufaces on the flywheel and pressure plate. However, by depressing a clutch pedal, the operator can withdraw the pressure plate against the bias of its spring and thereby disengage the clutch disk from the rotating friction surfaces of the flywheel and pressure plate. The clutch disk is carried by a splined shaft, which extends from the transmission and indeed constitutes the power input shaft for the transmission, so when the clutch pedal is depressed, the engine is disengaged from the transmission and the drive wheels located beyond it.
While the conventional clutch is quite suitable for automobiles operated under normal driving conditions, it does not lend itself to the rigors of automobile racing. In the first place, the conventional clutch concentrates much of the clutch mass a substantial distance from the axis of the crankshaft and thus produces a relatively high moment of inertia which retards acceleration. As a consequence, the engine does not respond as quickly to the accelerator as it might otherwise. Secondly, the conventional clutch relies solely on friction to transfer the power from the engine to the transmission, but the engines for racing vehicles develop considerably more torque than conventional engines--torque which is utilized in the demands of racing. Often the torque exceeds the ability of the friction surfaces to resist it, and the clutch slips. The problem is particularly acute in dirt track racing where the vehicles encounter irregular surfaces which impose substantial variances in the torque demanded from the engine.
The limitations of conventional clutches have lead to the development of specialized clutches designed specifically for racing. A typical clutch of this character transmits the torque from the engine through both a friction coupling and also through a direct connection. The former is called upon to set the vehicle in motion, whereas the latter is used during continued operation. This type of clutch may likewise be controlled with a clutch pedal, but the pedal operates somewhat differently, in that its neutral or disengaged position is intermediate its fully depressed and fully released positons. Indeed, when the pedal is fully depressed, the clutch engages through its friction surfaces, and when fully released, it engages through its direct coupling. This type of clutch may also be controlled by a hand apparatus.
One racing clutch of this variety utilizes a single pressure plate and clutch disk and calls upon them to transmit the full torque during acceleration as the vehicle is set in motion. This places severe demands on those components. Moreover, the clutch is about as large as a conventional clutch, and thus has a high moment of inertia. Another variety is somewhat smaller, and it has conical friction surfaces that is a cone clutch, for the initial engagement to set the vehicle in motion. But cone clutches have little surface area and wear out more rapidly than disk-type clutches.
The present invention resides in an automobile clutch that utilizes a plurality of friction plates arranged in a stack to initially engage an engine with its transmission. It also has lugs and cutouts arranged in two circular rows. When the lugs engage the cutouts, a direct coupling exists through the clutch, so that torque is transmitted without any slippage.